I. FIELD OF THE INVENTION
The present invention relates to batteries. More particularly, the present invention relates to a battery charger having a variable current output.
II. DESCRIPTION OF THE RELATED ART
The present capacity problems of the analog cellular radiotelephone system, advanced mobile phone system (AMPS), has necessitated development of other cellular technologies to relieve this burden. These new digital systems include the time division multiple access (TDMA) and the code division multiple access (CDMA) systems.
While the new cellular systems are coming on line, there are going to be many more AMPS systems than any of the new digital systems. Therefore, in order for a user to be able to use a radiotelephone in multiple service areas, the telephone must be able to operate in the AMPS system as well as one of the digital cellular systems; thus requiring newly designed radiotelephones to be dual mode.
Each type of cellular system has different power requirements. For example, an analog type AMPS radiotelephone typically transmits at higher power levels than a typical CDMA radiotelephone. This puts greater power demands on the battery or other device powering the unit.
If the radiotelephone is connected to a battery charger for recharging and the radiotelephone is operating while connected, the radiotelephone may require more power from the charger to operate properly while simultaneously charging the battery. Also, since the radiotelephone has the capability of operating in multiple systems, it is going to require a greater power output from the charger when it is operating in the AMPS mode as opposed to the CDMA mode. There is a resulting need for a battery charger that can change its output current in response to the mode of the radiotelephone.